Diorgano-(alkoxy) tin halides



United States Patent 3,470,221 DIORGANO-(ALKOXY) TIN HALIDES RajendraNath Chadha, Ann Arbor, and Kailash Chandra Pande, Adrian, Mich.,assignors to Staulfer Chemical Company No Drawing. Filed Sept. 2, 1965,Ser. No. 484,769 Int. Cl. C07f 7/22; B01j U.S. Cl. 260429.7 4 ClaimsABSTRACT OF THE DISCLOSURE Certain organomonoalkoxy halides arepresented as novel compounds and their use as catalysts in roomtemperature vulcanizing systems demonstrated.

This invention relates to a novel class of tin compounds and toorganopolysiloxane compositions incorporating such compounds.

The compounds herein were prepared with the object of providing animproved curing agent for silicone elastomers. In this connection, theirmost specific application has relation to compositions of the aboveindicated character which, with the aid of the tin compound, are adaptedto cure at temperatures ranging from about 20 to 40 C. Such compositionsare commonly referred to in the art as room temperature curing orvulcanizing compositions and are used for example, in mold making and inthe construction industry for caulking. They are commonly laid down asfrom a pot or tube in a liquid or plastic condition and subsequentlyharden in situ to a desired solid elastic state.

A tin compound conforming to the invention is embraced by the typeformula:

in which R is a hydrocarbon group e.g. alkyl, aryl, alkaryl and alkenyl,or a halo-substituted hydrocarbon group as halo-alkyl; R is an alkylradical of from l-lS carbon atoms, preferably l-8 carbon atoms; and X ishalogen, preferably chlorine.

As exemplary of compounds embraced by the invention may be mentioned:dimethyltinmethoxychloride, diethyltinmethoxybromide,dibutyltinethoxyiodide, diphenyltinpentoxybromide,dipropyltinpropoxybromide, diheptyltinheptoxychloride,dibutyltinbutoxychloride, divinyltinhexoxychloride, bisZ-chlorobutyltinbutoxychloride, dibutyltinbutoxybromide and the like.

It has been determined that such compounds are readily prepared where Rcontains 4 or more carbon atoms by first reacting the corresponding tinoxide viz. R SnO with the appropriate alcohol to obtain thecorresponding dialkoxide:

This reaction is carried out at reflux temperatures in a suitablesolvent using an excess of the alcohol. The water produced incident tothe reaction is continuously removed. With removal of substantially allthe water the reaction is considered complete. The solvent and anyunreacted materials are then distilled off following which the pressureis reduced and the dialkoxide recovered by distillation.

In the above reaction, the solvent employed should have a boiling pointexceeding that of the alcohol reactant or any constant-boilingalcohol-water mixture which may form (e.g. n-butanol-water mixture, B.P.92 0.).

The dialkoxide produced as described is reacted with 3,470,221 PatentedSept. 30, 1969 the corresponding tin dihalide (R SnX to obtain thedesired alkoxy monohalide:

In this reaction equimolecular proportions of the reactants areemployed. These are mixed slowly and with caution. The reaction isexothermic and some temperature control is necessary where substantialamounts of the reactants are used. A solvent is generally not employedif at least one of the reactants is a liquid. The reaction proceedswithout the formation of byproducts in any appreciable amount and istaken as complete when the temperature of the reaction mixture dropssubstantially without external cooling.

Where R in the type formula supra contains less than four carbon atoms,the tindialkoxide may be produced, for example, by reacting acorresponding tin dihalide with an alcoholate comprising R viz:

Upon removal of the salt the dialkoxide is reacted with an additionalincrement of the dihalide to obtain the desired alkoxyhalide.

The tin compounds of the invention as applied to catalyze roomtemperature curing of organopolysiloxane compositions are efiective inminimal amounts, e.g. 0.1 to 0.7 part by weight per 100 parts of therubber composition. The tin compound may be added as such to the rubbermaterial or, for convenience, it may be first incorporated in a carrier.Such carrier may be a comminuted solid or a liquid, or it may compriseboth a solid component and a liquid component. As a component of therubber material, the carrier is usually inert, but it may be functional.A typical carrier-catalyst formulation is a paste of the followingcomposition:

Parts Methyl end-blocked siloxane fluid (2000 cps.) 450 Tin catalystFumed silica (thickening agent) 125 Zinc oxide (for pigmentation) 5 Sucha paste, by attenuating the catalyst, facilitates the mixing operationat the work site and provides latitude in that it does away with thenecessity of precise measure ment. Using the particular paste, 4-5 partsthereof are ordinarily added per parts of base composition.

The amount of catalyst or curing agent added to the base composition isdetermined by the requirements of the particular job, especially the potlife or working time required. In caulking, for example, the workingtime is more or less conventionally calculated as of the order of 2 to2%. hours. Thus, in this instance the catalyst is added in an amountwhich will not result in any substantial stiffening of the siliconerubber until after expiration of such period of time. Normally, therubber is tack-free within 4-6 hours following the caulking, issubstantially cured after 24 hours and completely cured after 7 days.These periods, of course, vary somewhat with changes in humidity andtemperature conditions. Thus a. faster cure results under conditions ofhigh temperature and high humidity.

Exemplary base compositions to which the catalyst herein have been addedwith excellent results are given below. The OH Fluid in each instancerefers to an organopolysiloxane having functional hydroxyl groups mostof which are attached to the terminal silicon atoms as illustrated bythe formula in which n is an integer sufficient to yield a materialhaving a viscosity of from about 1700 to about 2800 centipoises and amolecular weight of 6-8000.

Representative base compositions Ethyl silicate 4 S-micron silica(reinforcing agent) 65 Zinc oxide (pigmenting and reinforcing agent) 10It is to be understood that the invention herein is not limited in useto hydroxy end-blocked organopolysiloxanes, for it is applicable to anyorgano-siloxane composition in which the organosiloxane is capable ofpolymerizing or condensing at a temperature of 20-40 C. to yield anelastomeric or neo-elastomeric substance. Silicone rubber roomtemperature vulcanizing stocks conform, in general, to the formula XORSi'O(R SiO) SiR- OX where each R represents either a monovalenthydrocarbon radical such as alkyl, aryl, alkenyl, alkaryl, aralkyl orcycloalkyl, or a halogenated monovalent hydrocarbon radical as chloro-,bromoor fluoroalkyl, aryl or alkenyl, X is a hydrogen atom or any of R,preferably hydrogen, and n is an integer of at least 50. The operativepolymers vary from relatively low viscosity fluids to high polymericgums soluble in organic solvents. These materials are primarilydifunctional, but mono and trifunctional components may be present in anamount minor in relation to the amount of difunctional units.

Organic radicals answering to R in the immediately preceding typeformula include: methyl, ethyl, octadecyl, phenyl, diphenyl, anthracyl,tolyl, xylyl, ethylphenyl, methylnaphthyl, benzyl, phenylethyl,cyclopropyl, cyclobutyl, cyclohexenyl, vinyl, allyl and octadecenyl aswell as halogen substituted derivatives of such radicals includingchloromethyl, bromomethyl, fluoromethyl, perchloroethyl,chlorofluoroethyl, bromophenyl, 3,3,3-trifluoropropyl,a,a,a-tI'iCl1lOIOt0ly1, chlorobenzyl, chlorodifluorovinyl, andchloroallyl.

The siloxane polymers can be homopolymers, such as hydroxy end-blockeddimcthylpolysiloxane mentioned supra, or copolymers as hydroxy andalkoxy end-blocked dimethyl-phenylmethylsiloxane copolymers or mixturesthereof.

Cross-linking agents applicable to compositions incorporating thecatalyst of the invention are, in general, organosilicon compoundshaving more than two functional groups and conforming to the generalstructural formula R SiX where R has the same significance as in theformula XOR SiO(R. SiO),,SiR OX appearing above, each X is a reactivegroup capable of condensation with the XO- substituents in the siloxaneand m has an average value of from to 2. Likewise applicable, are thecorresponding siloxanes.

As exemplary of specific cross-linking agents which may be used in thepractice of the invention may be mentioned: (a) silanes such astriethoxysilane, methyl triethoxy silane and phenyl-tributoxysilane,-('b) siloxanes such as dimethyl-tetraethoxydisiloxane anddimethyl-diphenyl hexaethoxytetrasiloxane, (c) organopolysiloxane resinscontaining monomethyl, dimethyl and monophenyl units, (d)organo-hydrogen-polysiloxanes of the formula l. Ll. J. l

in which R is normally methyl or phenyl and X and Y are reactive groupsas hydroxyl or OSi(CH or the like. These latter compounds meet therequirement of polyfunctionality, since hydrogen is taken as afunctional group.

The cross-linking agent may also be (e) a polyalkyl silicate (note ethylsilicate in the formulations supra) or (f) products derived from silicicacid and containing reactive groups, as hydroxy or alkoxy groups boundto silicon atoms. Silicic acid obtained by hydrolyzing trichlorosilaneis applicable as is silicic acid csterified with an alcohol to formalkoxylated silicic acids.

The invention is further illustrated by the following examples which arenot to be taken as in anyway limitative thereof.

EXAMPLE I Bu SnO (264.3 gms.) and n-butanol (four-fold excess) intoluene (1500 ml.) were refluxed under constant stirring. As soon as thereaction mixture started refluxing, water was formed and continuouslycollected through a Dean Stark take-off head. In about 4-6 hours, almostall the water was collected. The toluene was then distilled off and theunreacted n-butanol was also recovered. Thereafter the reaction productwas distilled under reduced pressure to obtain dibutyltindibutoxide(yield =60%, B.P.=l35 C., at 4 mm. pressure).

8.8 gms. of the dibutyltindibutoxide was cautiously mixed with 7.2 gms.of dibutyltindichloride in the absence of a solvent. Heat was evolvedand in about l0l5 minutes a low melting solid, dibutyltinbutoxychloride,was obtained in almost quantitative yield.

7 gms. of the dibutyltindibutoxide was slowly and carefully mixed with 8gms. of dibutyltindibromide. Again, heat was evolved and a low meltingsolid product, dibutyltinbutoxybromide, was obtained.

EXAMPLE II The procedure of Example I is repeated starting withdiheptyltinoxide in lieu of dibutyltinoxide and n-heptanol instead ofn-butanol. This gives diheptyltindiheptoxide which on reaction withdiheptyltindichloride yields diheptyltinheptoxychloride.

EXAMPLE III The procedure of Example I is repeated starting withdiphenyltinoxide which is reacted with n-amyl alcohol to producediphenyltindipentoxide. Reaction of the latter with diphenyltindibromideyields diphenyltinpentoxybromide.

EXAMPLE IV The procedure of Example I is repeated starting withdivinyltinoxide in place of dibutyltinoxide and using nhexanol as thealcohol. This gives divinyltindihexoxide which on reaction withdihexyltindichloride yields divinyltinhexoxychloride.

EXAMPLE V A base composition designed for caulking was prepared asfollows:

10 parts by weight of hydroxy CnCHDlOCkCd fluid 1 part by weight ofethyl silicate 5.6 parts by weight of silica filler To one portion ofthe base composition was added .2 part by weight of thedibutyltinbutoxychloride. This cured the rubber to a tack-free conditionin about 2 hours, as calculated.

To a second portion of the base composition was added .2 part by weightof the dibutyltinbutoxybromide. The cure to a satisfactory tack-freerubber required about onehalf hour longer than in the case of thecorresponding chloride catalyst.

This example is particularly significant in that it shows that thebutoxy-halides are capable of providing a cure period of selectedduration. The control of cure time is a function of the relatively bulkyvand. non-hydrolyzable halo group which tends to slow the rate ofhydrolysis of the single alkoxy group. Assuming constant conditions, toextend the cure period it is onlynecessary to use lesser amounts of thecatalyst. Conversely, for a faster cure a greater quantity of thecatalyst is employed. In any case, one should take into account that asbetween the halides, the chloride acts faster than the bromide and thelatter faster than the iodide, for instance.

EXAMPLE VI An apparatus consisting of a 1 liter flask, dropping funnel,nitrogen inlet, condensor, stirrer and thermometer was set up, all ofthis equipment having been previously completely cleaned and dried.100,2 grams of dry ethyl alcohol was placed in the flask along with 26grams of cut metallic sodium, added slowly and with care. With some ofthe sodium already reacted, 100.2 additional grams of dry ethyl alcoholwas introduced with stirring and heating. A good sodium dispersionresulted and with further heating to reflux complete solution wasachieved with formation of NaOC H 148.2 grams of dibutyltindichloridedissolved in benzene was slowly added to the alcoholate over a period ofapproximately 1 hour. When addition .was complete the mixture wasmaintained at reflux temperatures for about 6 hours, whereafter it wasallowed to cool and settle under a dry nitrogen atmosphere. To removethe salt precipitate the reacted mixture was filtered under nitrogen,first through a Bucher funnel, then through a fine sintered glassfunnel. The clear solution was distilled to remove solvent, leaving aclear liquid having a dark wine color. When this was distilled undervacuum (1 mm.) the fraction boiling at 136 C. proved to bedibutyltindiethoxide.

When reacted in equimolecular ratio with a second portion ofdibutyltindichloride the diethoxide yields dibutyltinethoxychloridewhich acts in the manner of the compounds above to catalyze the curingof organopolysiloxane systems.

Incident to the experimentation culminating in the present application,several dialkyltindialkoxide, including dibutyltindibutoxide, wereinvestigated for their effectiveness as curing catalysts in siloxanecompositions. It was found that when used in amounts required for acomplete cure the dialkoxides worked so fast as to be impractical.

Differently stated, it was discovered that when the amount of thedialkoxide was reduced to the point where the catalytic action ceased atthe end of a period corresponding to an optimum cure period the tensilestrength, elongation at break, hardness, and other properties of thesilicone rubber were adversely affected for lack of a complete cure.With the compounds of the invention, a complete cure can be achieved ata curing rate which is optimum in the case of any particular field ofuse.

The presence of moisture, normally atmospheric moisture, has beendetermined as essential to proper curing of a siloxane compositionconforming to the invention. Thus, a silicone rubber formulationcomprising one of the alkoxy halides will not cure within any practicalperiod if completely protected for moisture. It is evident from thefindings on which this application is based that the catalyst by virtueof the ambient moisture is enabled to generate OI-I groups which providethe catalytic effect On becoming directly attached to the tin. Asindicated in the last paragraph of Example V, the speed of generation ofsuch groups is a function of the halide portion of the molecule which ina sense slows down the rate of hydrolysis of the more reactive alkoxyradical. It is believed that the mechanism of the hydrolysis is asillustrated below, with overlapping of the two reactions:

The invention claimed is:

1. A diorgano-, monoalkoxy tin halide in which the two organogroups areidentical, the same being selected from the class consisting of thephenyl radical and alkyl and alkenyl radicals of no more than 8 carbonatoms.

2. Dibutyltinbutoxychloride.

3. Dibutyltinbutoxybromide.

4. Dibutyltinethoxychloride.

References Cited UNITED STATES PATENTS 3,194,770 7/1965 Hostettler260-46.5 XR

TOBIAS E. LEVOW, Primary Examiner W. F. W. BELLAMY, Assistant ExaminerUS. Cl. X.R. 252-431 Disclaimer 3,470,22l.-Rajendra Nath Chad/la, AnnArbor and Kailash Chandra Pqnde, Adrian, Mich. DIORGANO-(ALKOXY) TINHALIDES. Patent dated Sept. 30, 1969. Disclaimer filed Apr. 9, 1984, bythe assignee, SWS Silicones Corp. Hereby enters this disclaimer to allclaims of said patent.

[Ojficial Gazette July 3. 1984.]

